The new WooCommerce email templates are using the additional content to add text at the end of the emails. However this field is not translatable with String translation. Please add this field also to String translation to let us translate the additional content also.
Hi Peter, this string can be added to the String Translation table from the admin texts. Go to WPML -> String Translation and at the bottom of the page, click "translate strings in admin texts". On this page, you will find the WooCommerce email settings. If you expand the section, you will see the additional content. Please note that this will only display here once the original additional content is update.
Please let me know if you need any further assistance and I will be happy to help.